Orthogonal Frequency Division Multiple Access (OFDMA) modulation schemes have been proposed for downlink transmissions over an air interface in next generation communication systems such as 3GPP (Third Generation Partnership Project) E-UTRA (Evolved UMTS Terrestrial Radio Access) and 3GPP2 Phase 2 communication systems. In an OFDMA communication system, a frequency channel, or bandwidth, is split into multiple contiguous Resource Blocks (RBs). A grouping of multiple RBs is known as a Resource Block Group (RBG). Each RB comprises multiple, for example, 12, contiguous frequency sub-carriers that are orthogonal to each other. Under the 3GPP E-UTRA standards, a Node B then assigns the RBs to users' equipment (UEs) on a sub-frame basis, wherein a sub-frame may have a duration of one millisecond (ms).
In order to maximize bandwidth usage, OFDMA communication systems may engage in frequency selective scheduling (FSS), wherein transmission errors are minimized by scheduling a user equipment (UE) for an RB only where the UE is known to have a good downlink channel. Accordingly, FSS requires narrowband channel feedback from the UE, wherein the channel quality reported is specific to each RB. That is, for any given Transmission Time Interval (TTI), the RBs are allocated to users based on measured channel conditions. The channel condition measurements are performed by a user equipment (UE), which UE measures channel conditions for each and every RB during a measuring period, such as a Transmission Time Interval (TTI) (also known as a sub-frame) or a radio frame transmission period. The UE then reports the measured channel conditions for the RBs to a serving Node B in a Channel Quality Information (CQI) message. Based on the reported CQIs, an OFDMA communication system is able to selectively schedule the RBs over a scheduling period, typically one or more TTIs or radio frames, and further adaptively determine appropriate modulation and coding schemes for each RB during the scheduling period. However, reporting a CQI for each and every RB may consume a significant amount of uplink system overhead, especially for OFDMA systems utilizing a 20 megahertz (MHz) bandwidth and employing as many as 100 RBs within that bandwidth.
Therefore, a need exists for a method and apparatus that provides channel quality information sufficient to adaptively assign RBs to UEs over a scheduling period and that does not consuming the overhead resulting from the reporting of CQI for every RB of the frequency bandwidth.